
// 功能: 显示帮助命令
void help(void)
{
printf("command: \n\
help   ---  show help menu \n\
clear  ---  clear the screen \n\
cd     ---  change directory \n\
mkdir  ---  make directory   \n\
create  ---  create a new file \n\
open   ---  open a exist file \n\
read   ---  read a file \n\
write  ---  write something to a file \n\
close  ---  close a file \n\
delete ---  delete a exist file \n\
format ---  format a exist filesystem \n\
logout ---  exit user \n\
rd     ---  delete a directory \n\
quit   ---  exit this system\n");
}